A typical known filling machine used in this sector substantially comprises a carousel conveyor rotating about a vertical axis, a product tank containing the pourable product and carried centrally by the carousel conveyor, and a plurality of filling devices supported by the carousel conveyors in positions radially external with respect to the product tank, connected to the product tank through respective fluidic circuits or lines and conveyed by the carousel conveyor along a circular transfer path.
In particular, the carousel conveyor receives a succession of empty receptacles from an input star wheel and releases the filled receptacles to an output star wheel.
Each filling device basically comprises a support device, adapted to receive and retain a respective receptacle in a vertical position, and a filling valve for feeding a given volume of pourable product into the receptacle as the filling device travels along the circular transfer path by following the rotary movement imparted to the carousel conveyor.
An example of known filling valve is disclosed in EP-A-1411023 and basically comprises:                a vertical tubular body fixed to the peripheral portion of the carousel conveyor and defining a central flowing channel for feeding the pourable product to a respective receptacle to be filled;        a shutter engaging in a sliding manner the tubular body and movable within the flowing channel to allow or prevent flow of the pourable product towards the respective receptacle; and        actuator means to move the shutter within the channel of the tubular body.        
In particular, the tubular body presents a longitudinal axis parallel to the carousel conveyor axis and terminates at a lower end with an axial outlet opening adapted to contact in use a top end mouth of a receptacle to be filled.
The channel of the tubular body comprises a tapered-section portion located at a given axial distance from, and above, the outlet opening and tapering towards the outlet opening itself up to a minimum-diameter section. From this point down to a position close to the outlet opening, the channel comprises an axial bottom end portion having a constant diameter equal to the minimum diameter of the tapered-section portion.
The shutter is movable within the channel of the tubular body between a lowered closed position, in which the shutter sealingly closes the tapered-section portion of the channel itself and interrupts flowing of the pourable product towards the axial bottom end portion and the outlet opening, and a raised open position, in which the shutter delimits with the tapered-section portion an annular passage communicating with the axial bottom end portion and the outlet opening.
The filling valve further comprises three conduits formed within the tubular body and arranged on outer circumferences than the central channel with reference to the longitudinal axis of the filling valve:                one exhaust conduit for discharging the gas present in the receptacle during filling thereof with the pourable product;        one decompression conduit for depressurizing the receptacle at the end of the filling, for carbonated products; and        one air conduit for forcing the pourable product present in the axial bottom end portion of the channel to fall down into the receptacle.        
In case of carbonated pourable products, the exhaust conduit is also used for pressurizing the receptacle at a desired pressure value, higher than the atmospheric pressure, prior to starting the actual filling of the receptacle itself.
The filling device disclosed in EP-A-1411023 has the following drawbacks.
First of all, the restricted passage (axial bottom end portion) connecting the tapered-section portion of the channel to the outlet opening tends to increase turbulence of the product delivered to the receptacle and to create vortices, with possible formation of undesired foam.
Moreover, due to the presence of such restricted passage, it is necessary to provide an additional air conduit and an additional air circuit to cause the product possibly left in the axial bottom end portion of the channel to fall down into the receptacle.
Finally, by using the same conduit for discharging the gas present in the receptacle during filling and for pressurizing the receptacle itself may cause some foam possibly left in the bottom portion of such conduit at the end of one filling operation to be delivered to the next receptacle during the following pressurizing step.